Drug eruptions are a frequent complication seen in approximately 2% to 3 % of hospitalized patients. Some of these eruptions have a characteristic clinical picture such as erythema multiforme, fixed drug eruption, vasculitis, or acute generalized exanthematic pustulosis. However, most patients present with less specific rashes such as morbilliform drug eruptions, or urticaria that can account for up to 95% of cutaneous drug reactions. The diagnosis of drug eruptions is based on clinical history, particularly when the rash is temporally related to the introduction of a new drug, in the last days or weeks. Most drugs that the patient had been taking for years can usually be excluded as triggering agents. In addition, the clinical features of the rash, and, in some cases, the histopathologic examination of a cutaneous biopsy can help in diagnosis.

Although some drug eruptions have histologic patterns that make them easily diagnosed, in most patients histology is ‘‘non-specific’’ or ‘‘non-diagnostic’’. In a study published in the December issue of the Journal of the American Academy of Dermatology the authors have made a revision of the of cutaneous drug eruptions diagnosed over a 5-year period. A total of 104 cases were included in the study. In 83% of the cases, the suspected drug or drugs could be narrowed to 3 or fewer. The two most frequent classes of drug associated with the appearance of a rash were antibiotics (45%) and antiepileptics (15%). 94% of the rashes were morbiliform. Most of the biopsies (80%) showed superficial dermal inflammatory infiltrates in a combined perivascular and interstitial pattern. There were interface changes in 53% of the biopsies. The inflammatory infiltrates was composed of lymphocytes only in 32% of the cases, lymphocytes and eosinophils in 29% of the cases, lymphocytes and neutrophils in 10% of the cases, and lymphocytes, neutrophils and eosinophils in 21% of the cases. Therefore, 50% of the cases contained eosinophils in the infiltrate. In summary, the finding of superficial infiltrates with or without interface changes, with the presence of eosinophils is the most frequent histologic pattern observed in morbilliform drug eruptions. (more…)

The excision of atypical pigmented lesions is a common practice in Dermatology. However, the correlation between clinical and histological atypia is many times poor and lesions that are clinically atypical turn out to be rather unimpressive histologically. Therefore factors that help to predict the probability of these lesions to be truly atypical or malignant can be useful in clinical practice. In this study published in the October issue of the British Journal of Dermatology, a group from Leeds has performed a retrospective study addressed to find what clinical data predicted severe histological dysplasia/early melanoma in excised atypical melanocytic lesions. There where 434 eligible patients with 189 benign melanocytic naevi, 98 with atypical naevi, 19 with Spitz ⁄Reed naevi, 22 blue or congenital naevi, 29 severely dysplastic naevi ⁄in situ melanomas and 77 invasive melanomas. The authors found that old age, history of clinical changes in the lesions, and site on an extremity where predictors of melanoma. An older age was the only predictor predictive of severe histological atypia (or melanoma in situ) compared mild to moderate atypical naevi. (more…)

Syphilis is a sexually transmitted disease that has re-emerged (primary and secondary syphilis in particular) in the late 1990s in western European countries. This is probably due to behavioural changes, probably driven by changes in the HIV epidemic. The diagnosis is usually based on serology, with a combination of nontreponemal and treponemal tests. However, these tests can be negative in early stages, and have low sensitivity and specificity. In addition, many young and middle-aged dermatologists have had relatively little clinical experience with syphilis. This fact can lower the diagnostic suspicion in some cases, and so syphilis serology is not performed. Therefore, new diagnostic tools will be important in the future. In the October issue of the Journal of Investigative Dermatology a group of French investigators studied the detection of Treponema pallidum in macular or maculo papular skin lesions from patients with secondary syphilis by using both PCR and immunohistochemistry with a polyclonal antibody against T. pallidum. The authors found the presence of T. pallidum in 92% of cases, demonstrating a good sensitivity when both techniques are combined. (more…)

Dermatofibrosarcoma protuberans (DFSP) is an uncommon locally aggressive spindle-cell neoplasm that frequently recurs and can even produce distant metastases. The diagnosis is based on histology, but in some cases it can be very difficult to differentiate DFSP from the much more frequent benign spindle-cell neoplasm dermatofibroma (DF). Immunohistochemistry can be useful to differentiate between both neoplasms as DFSP are usually CD34 positive and factor XIIIa negative; while DF are usually stain CD34 negative and factor XIIIa positive. However some cases cannot be differentiated with these stains, and therefore new markers would be useful. Stromelysin-3 was recently found to be useful as it would be positive in DF, and negative in DFSP. In this study published in the August issue of the British Journal of Dermatology, a group of Korean researchers studied 23 cases of DF and 17 cases of DFSP. They found that stromelysin-3 was expressed in all cases of DF, and only one case of DFSP was weakly positive. In addition, they found that this immunohistochemical stain had overall a better sensitivity and specificity than CD34 and factor XIIIa for the diagnosis of these spindle cell neoplasms. (more…)